1992 BMW 525i M50 engine idle problem

[bissellh]

My 1992 525i E34 M50 has an idle problem, but only after the engine warms up. When the engine is cold the idle is steady right around 600 - 700 RPMS. But, after the engine warms up to normal operating temperature, the idle bounces around between 1000 and 2000 RPMs.

I have no computer fault codes nor do I have a check engine light.

The first thing I did is replace the coolant temperature sensor. It just seemed like the logical place to start since the problem happens when the engine is hot. But, it did not resolve the problem.

I then observed that the hotter it is under the hood, the more the idle bounces around. The problem is not as bad on cold days. It also is not as bad after leaving the hood open for a while, eventhough the engine is still at normal operating temperature.

I checked voltage to the throttle position switch and resistance between the terminals as described in my repair manual. It checked out when the engine was cold and when it was hot.

I also cleaned the AFM with carb cleaner. That did not resolve the problem. I guess I should check the AFM according the my repair manual both at cold and hot temperatures too.

I replaced the ICV(idle control valve) with a used one not too long ago. I do not think it could be the problem. I would like to test it. I am not sure I can access it without removing my intake though.

According to my repair manual, I should also test my intake air temperature sensor.

Can I access my ICV without removing the intake? Where is my intake air temperature sensor? Is there anything else I should be looking at, such as the injectors, engine speed sensor, cylinder identifying sender, etc? Has anyone had a similar experience? If so, how was it resolved?

[Blitzkrieg Bob]

from under the car. just gotta apply some yoga to get into postion.

[BillionPa]

aint that MAF, that thing gets hot right away. if you have a thing of canned air spray it on the crank position sensor when the car starts jumping to see if thats whats causing the problem, if it is, the cold spray will shut it the hell up real fast.

[Blitzkrieg Bob]

aint that MAF, that thing gets hot right away. if you have a thing of canned air spray it on the crank position sensor when the car starts jumping to see if thats whats causing the problem, if it is, the cold spray will shut it the hell up real fast.

upside down

[bissellh]

aint that MAF, that thing gets hot right away. if you have a thing of canned air spray it on the crank position sensor when the car starts jumping to see if thats whats causing the problem, if it is, the cold spray will shut it the hell up real fast.

I will try that. But, first I have to figure out which sensor it is and where it is located on my 1992 BMW 525i M50 engine. According to my repair manual, I have a cylinder identifying sender, sometimes called a camshaft sender. It is located on the timing cover. I also have an engine speed sensor, sometimes called a crankshaft sensor. I am not sure where it is located.

I am guessing the crank position sensor and the engine speed sensor/crankshaft sensor are the same things. Do you know where I can find it on my engine so I can spray canned air on it?

[Blitzkrieg Bob]

Kills the car from the get go...no start just crank.

The fuel pump won't pump with out a CPS signal

[bmwrp8]

O2 sensor? hehehe just a guess check it anyway

[bissellh]

Kills the car from the get go...no start just crank.

The fuel pump won't pump with out a CPS signal

Do you think it is worth checking by spraying canned air on it anyway? paerhaps the signal is scewed once it heats up. Do you know where it is located on my 1992 BMW 525i E34 M50 engine?

[bissellh]

Do you know of a way I can check the O2 sensor myself???

[bmwrp8]

Do you know of a way I can check the O2 sensor myself???

I saw that post before on how to check your O2 sensor just do a search but try doing a stomp test or not use a code tool and pull out your codes might just be something else.